As is well-known, Ziegler-Natta catalysts can be used in olefin polymerization, and enable formation of highly stereospecific polymers at a high yield especially when being used in the polymerization of α-olefins having three or more carbon atoms. Solid titanium catalyst components in the Ziegler-Natta catalysts have magnesium, titanium, halogens, and internal electron donors as basic components. The development of internal electron donors, as an essential ingredient in the catalyst component, has promoted constant upgrading of polymerization catalysts, and meanwhile accelerated development of external electron donors. Currently, a large variety of electron donors have been disclosed, such as monocarboxylates or polycarboxylates, ketones, monoethers or polyethers, amines, and derivatives thereof as internal electron donors, and monocarboxylates, amines, aminosilane, and derivatives thereof as external electron donors.
In recent years, people are trying to develop new external electron donors to be used in olefin polymerization, so as to obtain catalysts of higher performance, and thus to develop polymers of difference performance.
WO2012052387 discloses a dicarboxylate compound comprising more than 4 carbon atoms, such as adipate and pimelate. Employment of a diol ester as the internal electron donor and a dicarboxylate as the external electron donor can significantly improve hydrogen response of the catalyst. Preparation of the dicarboxylate, however, is complex and of high costs due to long carbon chains therein.
The present disclosure aims to provide a catalyst composition of higher activity, stereospecificity, and hydrogen response, and polymers of wider molecular weight distribution can be obtained.